Water-vapor-permeable, watertight, and heat reflecting flat composite, process for its manufacture, and use thereof

ABSTRACT

A water-vapor-permeable, watertight, heat-reflecting flat composite is made by a process of combining a metal layer and a nonporous, water-vapor-permeable, watertight, hydrophilic flat substrate. The process includes at least the three steps of (1) selecting the substrate, (2) pre-cleaning the substrate, and (3) applying the substrate to the metal layer. Such a composite offers protection from heat loss, infrared-based detection, ultraviolet radiation, electro-smog, and static electricity.

This application is a continuation of application Ser. No. 09/943,148,filed Aug. 31, 2001.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a water-vapor-permeable, watertight,and heat-reflecting flat composite, a process for its manufacture, anduse thereof.

2. Description of Related Art

Water-vapor-permeable, watertight, and heat-reflecting composites madefrom a metal layer and a microporous membrane are known in the art. U.S.Pat. No. 5,955,175 describes a textile material produced by metallizinga microporous membrane. The metallization causes a reflection of thermalradiation. The metal forms a discontinuous layer on the surface and onthe pore walls of the microporous membrane that are adjacent to thesurface. Compared to the size of H₂O molecules, the pores of themicroporous membrane are very large, even in the metallized state, sothat the water-vapor permeability of the microporous membrane ismaintained even after it is metallized.

Water-vapor-permeable, watertight, and heat-reflecting composites madefrom a metal layer and a nonporous membrane, or from a nonporoussubstrate, have not yet been disclosed. In attempting the metallizationof a microporous membrane, as described in U.S. Pat. No. 5,955,175, witha nonporous membrane, it is observed that the adhesion between the metallayer and the nonporous membrane is very poor, i.e., that the metallayer peels off even after short use.

SUMMARY OF THE INVENTION

For this reason, it is an object of the present invention to provide aprocess for manufacturing a water-vapor-permeable, watertight, andheat-reflecting composite from a metal layer and a nonporous substrate,and to provide such a composite that at least reduces the aforementioneddisadvantage.

These and other objects are achieved by a process for manufacturing awater-vapor-permeable, watertight, heat-reflecting flat compositecomprising a metal layer and a nonporous, water-vapor-permeable,watertight, hydrophilic flat substrate, whereby the metal layer has asurface facing the substrate and a surface facing away from thesubstrate, and whereby the substrate has a surface facing the metallayer and a surface facing away from the metal layer, comprising atleast the following steps:

-   -   a) selecting the substrate,    -   b) pre-cleaning at least one surface of the substrate, and    -   c) applying the metal layer to the substrate surface facing the        metal layer.        The composites made by the process of the invention exhibit        adhesion between the metal layer and substrate that passes the        Tesa tape test.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As previously noted, in the case of the known metallized microporousmembrane, the pores of this membrane, which are very large compared toH₂O molecules, ensure its water-vapor permeability. In the metallizationof a nonporous water-vapor-permeable and watertight substrate, however,it was to be expected that a continuous metal layer that is no longerwater-vapor-permeable is formed on the substrate. This applies all themore, since it is known from the field of packaging films that films canbe provided with a thin metal layer that, as described inJP-A-11-279,306, already forms a vapor barrier at a thickness of about10 nm.

For this reason, it must be considered surprising that, in the form ofthe process of the invention, a composite made from a metal layer and anonporous substrate is rendered accessible that is not onlyheat-reflecting but is also water-vapor-permeable to a significantextent. It must be considered even more surprising that, with theprocess of the invention, composites can be provided that even under100% heat reflection exhibit a water-vapor permeability that is onlyslightly reduced compared to a non-metallized, nonporous substrate.

In a preferred embodiment of the process of the invention, a polyetherester, polyether amide, or polyether urethane film is selected as asubstrate in step a). The process of selecting the substrate may includesteps for preparing the substrate.

In another preferred embodiment of the invention, the substrate selectedin step a) is joined to a textile fabric, such as a woven, nonwoven, orknitted fabric, on the side facing away from the metal layer to beapplied in step c).

In another preferred embodiment of the invention, the substrate selectedin step a) is joined to a textile fabric, such as a woven, nonwoven, orknitted fabric, on the side facing the metal layer to be applied in stepc), the filaments of which are spaced apart. Spacing of the filamentsensures that a portion of the substrate surface is accessible for stepsb) and c).

In accordance with the invention, the substrate must be pre-cleaned instep b) prior to applying the metal layer in step c), whereby thepre-cleaning is preferably conducted on the side of the substrate thatis to face the metal layer to be applied in step c).

To pre-clean the substrate, a plasma treatment in oxygen has provensuitable for the process of the invention in order to achieve goodadhesion between the metal and substrate. For this reason, a plasmatreatment is preferably employed in the process of the invention,whereby the plasma treatment is conducted in a vacuum, preferably at apressure of about 1 mbar to about 0.001 mbar and more preferably at apressure of about 0.01 mbar to about 0.03 mbar.

Furthermore, for the pre-cleaning of the substrate in the process of theinvention, a plasma treatment in a gas containing oxygen is preferred,whereby it is especially preferred to use a mixture of about 10 to about50% oxygen by volume and about 90 to about 10% nitrogen by volume as thegas containing oxygen. According to the invention, air is highlypreferred as the gas containing oxygen, because the use of air resultsin good pre-cleaning of the substrate after only brief plasma treatment,such that the metal layer to be applied in step c) adheres to thesubstrate and passes the Tesa tape test.

In the context of the present invention, passing the Tesa tape testmeans that, when attempting to remove a strip of “Tesa” tape applied tothe metal layer of the substrate, either the substrate is lacerated orthe “Tesa” tape can be removed without destroying the substrate andwithout transferring metal with it.

In a preferred embodiment of the process of the invention, the plasmatreatment is conducted in air, especially preferably at atmosphericpressure, i.e., as a corona discharge. The advantage of this embodimentis that generation of a vacuum is not required. However, foreign gases,which can be present in the air of the laboratory or productionfacility, can interfere with the pre-cleaning process.

For this reason, in another especially preferred embodiment of theprocess of the invention, the plasma treatment is conducted in a mixtureof about 10% to about 50% oxygen by volume and about 90% to about 50%nitrogen by volume, or in air, in a vacuum. In this manner, thepenetration of foreign gases into the plasma is prevented, thus ensuringthat the plasma treatment indeed takes place only in a defined plasmagas.

Preferably, the vacuum is from about 1 mbar to about 0.001 mbar, andespecially preferably from about 0.01 mbar to about 0.03 mbar, since aparticularly brief pre-treatment is possible in these ranges.

The application of the metal layer in step c) of the process of theinvention is preferably performed by physical vapor deposition (PVD).This is a known coating technique and is described in L. Holland,“Vacuum Deposition of Thin Films”, Chapman and Hall, London (1966), forexample.

In the process of the invention, the metal layer is preferably appliedwith a thickness of about 10 nm to about 200 nm, and especiallypreferably with a thickness of about 30 nm to about 180 nm.

For applying the metal layer in the process of the invention, basicallyany metal can be used that can be applied using PVD. In the process ofthe invention, the metal layer applied is preferably Al, Cu, Au, or Ag,or an alloy of AgGe, CuZn, CuSn, CuAg, or CuAgSn, whereby the alloylayers have a higher corrosion resistance than the pure metal layers.The term “metal layers” thus includes alloys.

To protect the metal layer from oxidation, in a preferred embodiment ofthe process of the invention, a protective layer is applied to the metallayer after step c), whereby a protective layer made from a cross-linkedpolyurethane is especially preferred.

Furthermore, the underlying object of the invention is satisfied by awater-vapor-permeable, watertight, heat-reflecting flat compositecomprising a metal layer and a nonporous, water-vapor-permeable,watertight, hydrophilic flat substrate and producible according to thepreviously described process of the invention.

Furthermore, the underlying object of the invention is satisfied by awater-vapor-permeable, watertight, heat-reflecting flat compositecomprising a metal layer and a nonporous, water-vapor-permeable,watertight, hydrophilic flat substrate, whereby the metal layer has asurface facing the substrate and a surface facing away from thesubstrate, the substrate has a surface facing the metal layer and asurface facing away from the metal layer, and the metal layer adheres atleast predominantly to the substrate surface such that it passes theTesa tape test.

In the context of the present invention, the property that the metallayer at least predominantly adheres to the substrate surface such thatit passes the Tesa tape test means that adhesion of the metal layerpasses the Tesa tape test over nearly the entire substrate surfacefacing the metal layer. In this context, passing the Tesa tape testmeans that, when attempting to remove a strip of “Tesa” tape applied tothe metallized side of the composite, either the substrate is laceratedor the “Tesa” tape can be removed without destroying the substrate andwithout transferring metal with it.

In a preferred embodiment of the composite of the invention, adhesion ofthe metal layer passes the Tesa tape test over the entire substratesurface.

In a further preferred embodiment of the composite of the invention, thesubstrate is joined to a textile fabric, such as a woven, nonwoven, orknitted fabric, on the substrate surface facing away from the metallayer.

The underlying object of the invention is also satisfied by awater-vapor-permeable, watertight, heat-reflecting flat compositecomprising a metal layer and a nonporous, water-vapor-permeable,watertight, hydrophilic flat substrate, whereby the metal layer has asurface facing the substrate and a surface facing away from thesubstrate, the substrate has a surface facing the metal layer and asurface facing away from the metal layer, the substrate is joined on thesurface facing the metal layer to a textile fabric whose filaments arespaced apart, and adhesion of the metal layer passes the tape test bothon the filaments and between the filaments on the substrate surface.

In this context, passing the tape test means that, when attempting toremove a strip of “Tesa” tape applied to the metallized side of thecomposite, the “Tesa” tape can be removed without destroying thesubstrate and without transferring metal with it.

In a preferred embodiment of the composite of the invention, thesubstrate consists of a polyether ester, polyether amide, or polyetherurethane film.

Preferably, the metal layer of the composite of the invention is Al, Cu,Au, or Ag or an alloy of AgGe, CuZn, CuSn, CuAg, or CuAgSn.

The metal layer of the composite of the invention preferably has athickness from about 10 nm to about 200 nm, especially preferably fromabout 30 nm to about 180 nm, since in these ranges the composites of theinvention are highly water-vapor-permeable and heat reflecting.

In a preferred embodiment of the composite of the invention, the metallayer is provided with a protective layer on its surface facing awayfrom the substrate, whereby the protective layer is especially preferredto be a cross-linked polyurethane.

The composite of the invention is advantageously suited formanufacturing clothing that is not only watertight andwater-vapor-permeable but also offers the wearer all the protectivefunctions that the metal layer makes possible, such as protection fromheat loss and IR-based detection, protection from heat, UV radiation,and electro-smog, and protection from static electricity. In addition,the metal layer improves the aesthetic appearance for applications inwhich a metallic look is desirable, and it enables temperaturecompensation over the composite surface due to the thermal conductivityof metal.

An embodiment of the invention which yields an especially high value ofthermal insulation and which, therefore, is preferred, is constituted bya composite producible using a process of the invention or by acomposite according to the invention as described before, which ischaracterized in that on the surface of the metal layer facing away fromthe substrate or on the protective layer, a textile fabric is placed.The textile fabric exhibits a surface facing the metal layer or theprotective layer and a surface facing away from the metal layer or fromthe protective layer. Optionally on the textile fabric, on it's surfacefacing away from the metal layer or from the protective layer, a secondtextile material is placed. The optional second textile material may bemade of a material that is convection suppressing.

The textile fabric is selected from such materials which suppressconvection and which are formed in such a way that the surface of thetextile fabric facing the metal layer or the protective layer contactsonly a part of the surface of the metal layer or of the protectivelayer. In a preferred embodiment of the invention, the textile fabricsthat suppress convection and which are formed in such a way that thesurface of the textile fabric facing the metal layer or the protectivelayer contacts only a part of the surface of the metal layer or of theprotective layer can be knitted fabrics having an area density of about30 g/m² and a thickness of about 250 μm. The knitted fabrics preferablycontact about 20% of the surface of the metal or the protective layer.

The invention will be explained in more detail in the following example,but the present invention is not limited to this example.

EXAMPLE

In a receiver with a volume of 40 liters, a 10 μm thick polyether esterfilm, commercially available under the name SYMPATEX®, is affixed withadhesive tape in a specimen holder that is positioned 20 cm above atungsten helix with a charge of aluminum. The area of the film is 15×17cm. The receiver is evacuated to 0.00003 mbar. For pre-cleaning, aplasma treatment is then conducted with air as the reactive gas. Forthis purpose, air is fed into the receiver at a pressure of 0.02 mbar,and a plasma is ignited. The plasma has a frequency of 50 Hz and a powerof about 30 W. The plasma is left to act on the film for 60 seconds. Tometallize the pre-cleaned film, the receiver is subsequently evacuatedto 0.00003 mbar and the aluminum charge on the tungsten helix isvaporized by electrically heating the helix, forming an Al layer on thepolyether ester film. The thickness of the Al layer depends on theduration of Al vapor deposition.

The thickness of the Al layer is determined using ICP-MS (inductivecoupled plasma—mass spectroscopy). The aluminum in this case isdissolved in hydrochloric acid within a defined area of the metallizedfilm. The solution is metered as an aerosol, with argon as a carriergas, into a plasma torch, resulting in ion generation in the plasma gas.An aliquot portion of the plasma gas is passed to a mass spectrometer.In the mass spectrometer, the ions in the plasma gas are separatedaccording to mass and charge and quantified in a downstream detector.The thickness of the metal layer is determined by comparing with controlstandards. Composites were produced with an aluminum thickness of 15±4nm, 60±4 nm, and 150±13 nm (see Table). This was accomplished bysubjecting the SYMPATEX® films to Al vapor deposition for about 8, 30,and 75 seconds.

To determine the adhesion between the metal layer and the film in thethree composites, the tape test was conducted. A strip of “Tesa” tapewas applied to the metal layer. An attempt to remove the “Tesa” tapefrom the film resulted in no metal being transferred.

For further determination of the adhesion between the metal layer andthe film in the three composites, the composites were stored for 45minutes in water with a temperature of 50° C. After the composites wereremoved from the water, a cloth was used to rub the metallized side ofthe composites under slight pressure. Fault-free adhesion of thealuminum layer to the film was observed. Thereafter, the metallized sideof the composite was dried and a “Tesa” tape strip applied to themetallized side. An attempt to remove the “Tesa” tape from the filmresulted in no metal being transferred.

The aluminum thickness (d_(A1)), water-vapor permeability (WVP),measured according to ASTM E 96-66, method B with the modificationT_(water)=30° C., T_(air)=20° C., relative humidity=60%, and air flow of2 m/s, and the IR reflection (R_(IR)), measured in the wavelength rangefrom 2.5 to 10 μm, of the metallized SYMPATEX® films A, B, and C areindicated in the following table, whereby the range of error given forthe thickness is the maximum error resulting from two measurements.TABLE d_(Al) WVP R_(IR) Specimen (nm) (g/m² · 24 h) (%) SYMPATEX ® film0 3000 10 Metallized SYMPATEX ® film A 15 ± 4 2700 86 MetallizedSYMPATEX ® film B 60 ± 4 2600 97.5 Metallized SYMPATEX ® film C 150 ± 132200 100

The table shows that the metallized SYMPATEX® film C at 100% IRreflection nevertheless has a residual water-vapor permeability of 2200g/m²·24 h, which is reduced by only about one-fourth compared to thewater-vapor permeability of the SYMPATEX® film of 3000 g/m²·24 h.

1. A process for manufacturing a water-vapor-permeable, watertight, heatreflecting flat composite comprising a metal layer and a nonporous,water-vapor-permeable, watertight, hydrophilic flat substrate, whereinthe metal layer has a surface facing the substrate and a surface facingaway from the substrate, and wherein the substrate has a surface facingthe metal layer and a surface facing away from the metal layer,comprising at least the following steps: a) selecting the substrate, b)pre-cleaning at least one surface of the substrate, and c) applying themetal layer to the surface of the substrate facing the metal layer. 2.The process according to claim 1, wherein the substrate comprises apolyether ester, polyether amide, or polyether urethane film.
 3. Theprocess according to claim 1, wherein the substrate is joined to atextile fabric on the surface facing away from the metal layer to beapplied in step c).
 4. The process according to claim 1, wherein thesubstrate selected in step a) is joined to a textile fabric on thesurface facing the metal layer to be applied in step c), whereinfilaments of the textile fabric are spaced apart.
 5. The processaccording to claim 1, wherein the pre-cleaning in step b) is conductedon the surface of the substrate facing the metal layer to be applied instep c).
 6. The process according to claim 1, wherein the pre-cleaningin step b) comprises a plasma treatment in oxygen.
 7. The processaccording to claim 1, wherein the pre-cleaning in step b) comprises aplasma treatment in a gas containing oxygen.
 8. The process according toclaim 7, wherein the gas containing oxygen comprises a mixture of about10% to about 50% oxygen by volume and about 90% to about 10% nitrogen byvolume.
 9. The process according to claim 7, wherein the gas containingoxygen is air.
 10. The process according to claim 9, wherein the plasmatreatment is conducted at atmospheric pressure.
 11. The processaccording to claim 9, wherein the plasma treatment is conducted in avacuum.
 12. The process according to claim 11, wherein the vacuum has apressure of about 1 mbar to about 0.001 mbar.
 13. The process accordingto claim 12, the vacuum has a pressure of about 0.01 mbar to about 0.03mbar.
 14. The process according to claim 1, wherein the applying of themetal layer in step c) to the surface of the substrate facing the metallayer is performed by physical vapor deposition.
 15. The processaccording to claim 1, wherein the metal layer has a thickness of about10 nm to about 200 nm.
 16. The process according to claim 1, wherein themetal layer has a thickness of about 30 nm to about 180 nm.
 17. Theprocess according to claim 1, wherein the metal layer is comprised ofAl, Cu, Au, or Ag or an alloy of AgGe, CuZn, CuSn, CuAg, or CuAgSn. 18.The process according to claim 1, wherein the process further comprisesapplying a protective layer to the metal layer following step c). 19.The process according to claim 18, wherein the protective layer is across-linked polyurethane.
 20. A water-vapor-permeable, watertight,heat-reflecting flat composite comprising a metal layer and a nonporous,water-vapor-permeable, watertight, hydrophilic flat substrate, made bythe process according to claim
 1. 21. A water-vapor-permeable,watertight, heat-reflecting flat composite comprising a metal layer anda nonporous, water-vapor-permeable, watertight, hydrophilic flatsubstrate, wherein the metal layer has a surface facing the substrateand a surface facing away from the substrate, the substrate has asurface facing the metal layer and a surface facing away from the metallayer, and the metal layer adheres at least predominantly to thesubstrate surface such that it passes a Tesa tape test.
 22. Thecomposite according to claim 21, wherein the adhesion of the metal layerpasses the Tesa tape test over the entire surface of the substrate. 23.The composite according to claim 21, wherein the substrate is joined toa textile fabric on the surface facing away from the metal layer.